The chemical conjugation of specific benzo[a]pyrene oxides and other epoxides to glutathione, enzymatically and non-enzymatically, is being investigated using nuclear magnetic resonance (NMR) spectroscopy, chemical synthesis, and high pressure liquid chromatography (HPLC). The regiospecificity and stereo-specificity of the conjugation reaction is being determined. Procedures for the synthesis of thioether metabolites of various epoxides have been modified to allow large scale preparations. The stereochemistry of the reaction of glutathione with styrene oxide catalyzed by purified rat liver glutathione transferases has been established, and an active site geometry has been proposed to account for the stereoselectivity observed in enzyme mediated reactions.